The present invention relates to an improved pen needle and safety shield system particularly, but not exclusively, adapted for pen injectors. The safety shield system of this invention includes a retractable generally tubular shield which is spring biased to normally enclose the needle cannula of a pen needle dispenser, but which locks in the extended position enclosing the needle cannula following injection. Further, the double ended needle cannula assembly may be safely nested in the cup-shaped cap following injection for disposal.
Hypodermic syringes have been used for many years to deliver selected doses of fluids including liquid medicaments, inoculations, etc. to patients. However, many applications using hypodermic needles are self-administered, including, for example, insulin, anti-histamines, et cetera. The required manipulation of a standard prior art hypodermic syringe can be inconvenient, particularly where the injection is self-administered in a public environment. Medication delivery pens or pen injectors have therefore been developed to facilitate self-administration of injections. A typical pen injector includes a generally tubular body portion resembling a fountain pen which receives a vial of fluid, such as insulin, anti-histamines, et cetera, having a pierceable closure, such as a rubber septum. The pen needle includes a hub generally having a double ended needle cannula including a first end which extends into the body portion of the pen injector for piercing the closure of the vial and a second end used for self-injection of the fluid contained in the vial. The pen needle also generally includes a removable cup-shaped cap which encloses the second end of the needle cannula prior to use.
Various improvements in pen needles have been developed or proposed by the prior art since its introduction, including adjustable injection length pen needles as disclosed in U.S. Pat. No. 5,944,700 assigned to the assignee of the present application and safety shield systems for such pen needles, wherein the shield is generally cup-shaped including an open end which receives the body portion of the pen needle and a generally closed end portion having a central opening which receives the second end of the needle cannula when the shield is retracted from a first position enclosing the second end of the needle cannula to a second position wherein the needle cannula is exposed for injection. The assembly may further include a spring that biases the shield to the normally enclosed first position prior to injection.
Various safety shield systems have also been developed or proposed by the prior art for conventional hypodermic syringes wherein a tubular shield is spring biased to enclose the needle cannula following injection and including safety shields which lock in the extended enclosed position following injection. Such safety shield systems for conventional hypodermic syringes are operated manually or are spring biased to extend the tubular shield and enclose the needle cannula following injection but all require additional action (active systems,) such as force, to activate as compared to the standard injection process. Hand manipulated safety shield systems may include spiral or complicated channel-shaped tracks on an inside surface of the shield which guide the shield during extension of the shield to enclose the needle cannula and lock the shield in the extended position. However, such complicated track systems may not always be reliable.
A safety shield system for pen needles has not yet been developed wherein the shield initially encloses the second end of the needle cannula prior to use, permits retraction of the shield for self-administration of the fluid in the pen needle dispenser and then extends and locks the shield in the extended position enclosing the needle cannula following use. It would also be desirable to simplify the operation of the shield to eliminate manual manipulation or rotational movement of the shield from the retracted position to a locked extended position.
One problem with other pen needle accessories, such as hidden needle adapters, has been potential needle sticks to the user during assembly of the accessory on the pen injector. Because the shield must be retractable for injection and the shield and cap assembly is typically threaded on the pen needle dispenser, the natural tendency of the user or patient is to press the cap toward the injector during assembly. This may cause the needle to pierce the cap and possibly puncture the user during assembly. Another problem associated with pen needles has been the safe disposal of the hub and double ended needle cannula. It would be most desirable to safely enclose both sharp ends of the needle cannula hub assembly to avoid inadvertent punctures during and following disposal. As will be understood, one end of the needle cannula may be enclosed in the cup-shaped cap; however, the other end is exposed following removal of the hub assembly from the pen injector.
The pen needle and safety shield system of this invention solves these problems by providing a safety shield which normally encloses the needle cannula prior to use, permits retraction of the safety shield during injection and automatically extends and locks the shield in the extended enclosed position following use. The pen needle of this invention also prevents retraction of the shield during assembly of the shield and needle cannula and hub assembly on the pen injector. Further, the improved safety shield system of this invention permits safe disposal of the hub and double-ended needle cannula assembly following removal from the pen injector.